In recent years, with the growing of the technologies, lot types of electronic products are produced. The high-tech electronic devices are deeply combined with human's daily life. For example, each of the panels and the global positioning systems of automobiles, smart phones, tablet PCs, variety toys and remote-controlled apparatuses is part of the technology life of human nowadays. The mainly necessary elements in electronic devices are semiconductor elements, such like power semiconductors, transistors, amplifiers and switches, especially the power semiconductors are much more fabricated in industry.
For example, one of the common power semiconductors is an insulated gate bipolar transistor (hereinafter “IGBT”). The basic encapsulation of an IGBT is a power semiconductor with three terminals. The characteristics of IGBTs include high efficiency and high switching speed. Generally, IGBTs are developed to replace the bipolar junction transistors (or called BJTs). IGBTs have both the characteristics of field effect transistors (or called FET) and bipolar transistors, so the IGBTs can withstand high current load, the gate can be easily driven and the turn-on voltage drop is low. Under this circumstance, the common uses of IGBTs are applied to high-capacity power devices like switching power supplies, motor controllers and induction cookers.
Nevertheless, even though IGBTs have been fabricated and used for tens of years, there are still some drawbacks of the process technology and semiconductor structure. Please refer to FIG. 1. FIG. 1 schematically illustrates the structure of a conventional insulated gate bipolar transistor of the prior art. A conventional trench punch-through IGBT includes a metal oxide semiconductor (or called MOS) layer 11, a N-type buffer layer 12 and a P-type injection layer 13. The MOS layer 11 is disposed between an emitter metal layer 111 and a N-type drift layer 112 for providing electron injection and controlling element switching. The N-type buffer layer 12 is used for conducting between the electrons and the electron holes and withstanding high voltage. In addition, the N-type buffer layer 12 is used for buffering the electric field and adjusting the concentration of the electron hole injection, and the P-type injection layer 13 is used for providing electron hole injection, among which the P-type injection layer 13 is a high-concentration P-type substrate. As to the MOS layer 11, the carrier concentration must be increased whenever the turn-on voltage needs to be decreased. However, the amount of channel and the current density can only be increased to provide more injection electrons for the structure of the conventional IGBT.
On the other hand, because the N-type buffer layer 12 and the N-type drift layer 112 are fabricated through epitaxy in the processes of manufacturing the conventional IGBT 1, the total substrate cost is relatively higher and the characteristics of elements are not easy to be adjusted. Moreover, the carrier concentration of the collector metal layer 131 of the P-type injection 13 is relatively higher, so that the carriers are not easy to disappear when the element is turn-off. In other words, the extra carrier lifetime killing process is utilized to reduce the energy losses during the on-off operation, and the fabricating time and cost are simultaneously increased.
There is a need of providing a power semiconductor and a manufacturing method thereof to obviate the drawbacks encountered from the prior art.